Lack of 'equal' conditions at Turkey polls: OSCE

International observers on Monday said voters enjoyed a genuine choice in Turkey's twin presidential and parliamentary elections but denounced the lack of "equal" conditions for candidates to campaign.

President Recep Tayyip Erdogan swept the presidential polls in the first round on Sunday while his ruling Justice and Development (AKP) Party-led alliance won an overall majority in parliamentary elections, in initial results.

An executive presidential system approved by referendum in April 2017 now comes into force giving Erdogan expanded powers, which opponents say will lead to one-man rule.

"Voters had a genuine choice despite the lack of conditions for contestants to compete on an equal basis," the joint mission of the OSCE Office for Democratic Institutions and Human Rights (ODIHR) and the Parliamentary Assembly of the Council of Europe (PACE) said.

The mission found polling day procedures were "generally followed", but pointed to issues over counting and tabulation during which "legally prescribed steps were often omitted".

The Organisation for Security and Co-operation in Europe also said in a statement that in 10 percent of its observations, ballot box committees did not stamp the ballots.

However, the mission said voters had a genuine choice during what was a "vibrant" campaign in "a highly polarised political environment".

Earlier on Monday, Erdogan's main rival Muharrem Ince conceded defeat and said he accepted the election results, despite an "unjust" campaign.

Five candidates ran against Erdogan including the pro-Kurdish Peoples' Democratic Party (HDP) jailed ex-leader Selahattin Demirtas.

The OSCE noted there had been attacks and disruption, mainly against the HDP.

The observers referred to Erdogan and the AKP's "notable advantage", saying it was reflected in "excessive" coverage by state and private media.

The elections took place under a state of emergency in place since the 2016 attempted coup against Erdogan, which the OSCE said "limited" freedoms of expression and assembly.